The present invention relates to a process of enzymatically hydrolysing protein material to give a hydrolysate which is substantially free of a bitter taste.
Hydrolysed proteins, which are widely used in the food industry, may be prepared by hydrolysis of protein material with acid, alkali or enzymes. However, on the one hand, acid or alkaline hydrolysis can destroy the essential amino acids produced during the hydrolysis thus reducing the nutritional value, whereas enzymatic hydrolysis with proteases rarely goes to completion so that the hydrolysed protein contains substantial amounts of peptides and, depending on the nature of the protein and the enzyme used for proteolysis, the peptides formed can have extremely bitter tastes and are thus organoleptically undesirable.
Various methods have been tried to overcome the problem of bitter tasting peptides. For instance, European Patent Application No. 223560 claims a method for flavour control of a protein hydrolysate which comprises selecting a proteinaceous feedstock, subjecting said feedstock to a primary enzymatic hydrolysis with a proteinase to produce a primary hydrolysate including bittering substances, characterised by subjecting said primary hydrolysate to a secondary enzymatic hydrolysis with an extract containing aminopeptidase enzymes, said secondary enzymatic hydrolysis acting to convert said bittering substances at least to flavour-neutral substances. Examples of proteinaceous feedstocks described are soya protein, gluten, whey protein, casein, haemoglobin, yeast extract, cereal proteins, milk, milk powder, skimmed milk, potato extracts and microbial derived proteins. The only method described for the production of the aminopeptidases is by extraction from streptococcus lactis, but this extract may contain contaminating protease which can further generate bitterness by hydrolysing any proteins left in the substrate.
We have found that some proteolysed cheese products, such as Swiss cheese or cheddar cheese, when subjected to hydrolysis with extracts of protease and aminopeptidase, retain their bitter taste.